The underwater cleaning robot can conduct the cleaning operation without discharging the pool water, thus avoiding any hinderance in using the pool due to the operation, such that onerous work of cleaning the pool is reduced and the precious water resource is saved. Since the cleaning robot can do the cleaning work automatically, it got popular among vast consumers, and has a broad market place. However, since the capacity of the trash can of the cleaning robot is limited, after the cleaning robot works for a certain period of time, the user needs to remove the garbage and dust in the trash can manually. Thus, it is necessary to design an underwater cleaning robot which has a trash can that is easy to be detached by the user and has a good fitting accuracy and sealing.